This invention relates generally to apparatus which provides easily removable electromagnetic shielding and more particularly to such shielding employing opposing cantilever spring fingers specially adapted to miniature electronic equipment such as portable radiotelephones.
Radios, computers, and other electronic equipment often generate electromagnetic signals in one portion of the electronic equipment which may radiate to and interfere with another portion of the electronic equipment. To minimize this interference effect, electrically conducting (and sometimes magnetically conducting) material is interposed between the two portions of the electronic circuitry. This shielding may take the form of a wall or a complete enclosure and may be placed around the portion of the electronic circuit generating the electromagnetic signal and/or may be placed around the portion of the electronic circuit which is susceptible to the electromagnetic signal.
Classically, a sheet of copper may be formed in a configuration which may be soldered to the electronic circuit in a position where it will perform a shielding function. Such a permanent attachment usually requires space in the electronic circuit for secure attachment and is difficult to remove if the need for service arises. It is also common to use an entire housing which is cast or molded to enclose the electronic circuit to provide the desired shielding. This solution is often used when large areas needing shielding are involved but requires a significant amount of space. The use of spring fingers as part of the shielding technique has been employed in devices having removable shields but such fingers, because they do not oppose each other, place a mechanical bias on the fingers which must be compensated either by the mass of the shielding or by some other elements in the shielding. Cantilevered opposing spring contacts of connectors have been used in some connectors but only independently on each individual pin. The difficulty of providing connection over a relatively large area, such as a shield surface, has not been addressed.
Thus, miniaturized electronic devices place even greater constraints on shielding, first, because the electronic circuits are closer together, and second, the physical room available for shielding is greatly reduced. The techniques for attaching or surrounding the electronic circuit to the shielding must consume as little space as possible while providing secure, easily manufactured, and easily repairable interconnections.